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A141507 Number of n X n binary matrices, symmetric under 90-degree rotation, with no more than 2 ones in any 2 X 2 subblock. 0
1, 2, 1, 5, 7, 49, 93, 1237, 4141, 89949, 498037, 18459425, 173151965, 10776871089, 170022693228, 17856702680623, 475042622997955, 84045266807297263, 3767160477564182682, 1123350438602153100399, 84860275331624989832681, 42642871075536884664453747 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..21.

CROSSREFS

Sequence in context: A279508 A175770 A268950 * A193603 A059274 A082635

Adjacent sequences:  A141504 A141505 A141506 * A141508 A141509 A141510

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 10 2008

STATUS

approved

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Last modified April 21 22:12 EDT 2019. Contains 322328 sequences. (Running on oeis4.)